A former Contra Costa County deputy sheriff conducted five "dirty DUI" arrests on behalf of a Concord private investigator and accepted a bribe in at least one case, according to new felony charges filed by prosecutors Friday.

Stephen Tanabe, 47, of Alamo was arraigned in a Martinez courtroom on three counts of obstruction of justice, making false arrests and selling steroids. Tanabe, who was arrested on March 4 on unrelated drug and gun charges, remains out of custody on $260,000 bail.

Prosecutors also announced the dismissal of 10 cases connected to state drug agent Norman Wielsch, the former commander of an anti-narcotics unit arrested on Feb. 16 after authorities charged him with stealing drugs from county evidence lockers.

District Attorney Mark Peterson said his office determined Wielsch was no longer a credible witness in those cases. Wielsch, 50, has pleaded not guilty to 25 felony counts of stealing and selling methamphetamine, marijuana, steroids and prescription pills.

Peterson's office also dropped five pending criminal cases where Tanabe was the arresting officer. The dismissals did not include the five alleged "dirty DUI" stops, which were never filed by prosecutors. The men arrested in those cases will never face charges, prosecutors said.

"We had to drop the cases because we found it was unlikely he would be able to provide testimony due to the criminal charges he's facing," Peterson said of Tanabe.

Tanabe's attorney, Tom McKenna, did not respond to requests for comment.

Tanabe is the fourth Bay Area officer implicated by authorities because of ties to private investigator Christopher Butler, 49, a former Antioch police officer.

Butler was arrested along with Wielsch, his longtime friend. Authorities alleged that Wielsch stole drugs from evidence lockers and handed them off to Butler, who found buyers through his firm, Butler and Associates.

Conspiracy alleged

Both men pleaded not guilty and are due in court April 21, along with Tanabe.

On Friday, prosecutors alleged that Wielsch, Butler and Tanabe all conspired to sell steroids, which were first allegedly stolen from evidence bins by Wielsch.

Wielsch attorney Michael Cardoza said his client has worked with investigators and has taken responsibility for his actions.

Butler attorney William Gagen declined to comment on the new charges, citing the investigation.

In the new complaint, investigators also alleged that Tanabe accepted a bribe from Butler for the Nov. 2 arrest of an Oakland man selected by one of Butler's clients.

Butler was hired by the man's wife to arrange the arrest to smear the man's criminal record, prosecutors say. The man was lured to Meenar's Bar in Danville, where he was approached by attractive women who drank with him and suggested he follow them home.

'Dirty DUI' arrest

According to prosecutors, an off-duty Tanabe was inside the bar with Butler to watch the target. Before the man left the bar and got into his car, Tanabe called another deputy sheriff and asked him to make the drunken driving arrest. The man was booked into jail.

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Prosecutor Harold Jewett said in that incident Tanabe accepted a bribe from Butler for arranging the arrest, but would not say how much Butler paid.

Tanabe, who owned a private investigator's license and worked for Butler before he was hired by the sheriff's office, resigned from the department in March.

In a search-warrant affidavit filed last month, a sheriff's investigator wrote that two of Tanabe's colleagues said Tanabe had talked of making drunken-driving arrests to "dirty" someone's criminal record.

According to one colleague, Tanabe referred to the stop as a "dirty DUI."

District attorney Peterson said more such arrests are possible. "This investigation is continuing, and we'll follow it wherever it goes," he said.